Controlled cooled gaseous discharge luminaire



DeC- 29, 1954 E. F. scHRAlTH ETAL 3,163,356

CONTROLLED COOLED GASEOUS DISCHARGE LUMINAIRE BW JW@ 5 Sheets-Sheet 2 DeC- 29, 1964 E. F. scHRAlTH ETAL.

coNTRoLLED cooLED GAssous DISCHARGE LUMINAIRE Filed June 26, 1961 Dec. 29, 1964 E. F. scHRAlTH ETAL 3,163,366

coNTRoLLED cooLED GAsEous DISCHARGE LUMINAIRE 5 Sheets-Sheet 3 Filed June 26, 1961 I. l mw IQ l A a INVENTORS, 50a/,4R0 F, 5CH/QW 7W United States Patent O .3,ld3936d CNTRLLED -CLED GASEUS nlSQHARGE LUMNAERJE Edward F. Scln'aith, San Diego, Calif., and Harold A.. Van Dilsen, Jr., South Milwaukee, Wis.9 assignors to lldcGraw-lidison Company, Milwaukee, Wis., a corporation of Delaware Filed .lune 2o, 196i, Ser. No. llhdd 15 (Cl. 2do-whlt) This invention relates to outdoor' street and area lighting luminaires, more particularly it relates to luminaires incorporating gaseous discharge lamps the light output of which is maintained by the controlled cooling of a minute spot or localized portion of the lamp bulb wall.

The theory of controlled spot cooling of gaseous discharge lamps is explained in a co-pending application Serial No. 859,455, entitled Cooling Fluorescent Lamps, of Philip B. Clark and Harold A. Van Busen, lr., which was tiled on December 14, 1959, Aand is assigned to the assignee of this application. One of the mechanisms disclosed in that application for `achieving controlled spot cooling includes a number of thermoeleetric elements of the Peltier type. The thermoelectric elements are connected to a cold junction metal shoe which is in contact with and conducts heat away from a localized portion of the lamp bulb wall. Also connected to the thermoelectric elements are a plurality of heat dissipating tins so that heat is conducted away from the cold junction to the heat dissipating uns and a heat transfer relationship is maintained between 4the metal shoe and the lamp bulb wall. Included in the cooling mechanism is a thermostat which controls the power source supplying the thermoelectric elements and which is sensitive to the temperature of the portion of the lamp bulb wall being cooled. In this manner the minute spot or localized portion oi the lamp bulb wall can be maintained at a predetermined temperature to maintain optimum light output of the gaseous discharge lamp.

For the purposes of this application it is deemed suliicient to discuss the theory of spot cooling generally, with reference being made to application Serial No. 859,455 for a more complete discussion. The light output of a gaseous discharge lamp, such as a fluorescent lamp, is dependent upon the pressure of the mercury vapor within the lamp which is in turn dependent upon the temperature of the lamp. lt has been discovered that the pressure of the mercury vapor will in fact be determined by the coolest spot on the lamp bulb wall. By cooling and maintaining this spot on the lamp bulb wall at a predetermined temperature corresponding to the temperature at which optimum light output occurs, the light output of the lamp can be maintained at an optimum value.

Within the luminaire there are sources of temperature variations, other than the localized portion being controlled, which can influence the thermostat which is used to control the power source supplying the thermoelectric unit. For eicient operation of the spot cooling mechanism the iniiuence of such other temperature sources on the control means should be kept at a minimum. Further, a good heat transfer connection should be maintained between the lamp bulb Wall and the cold junction oi the spot cooling mechanism to insure efficient heat transfer therebetween; however, this heat transfer connection should be accomplished without exerting excessive pressures upon the lamp bulb wall which would produce stresses in the bulb wall and, further, without contact of the lamp bulb with rough and/or sharp edges. Also, provision should be made for removing heat from the heat dissipating fins so `that the ns will be capable of receiving and storing the heat conducted from the cold junction by the thermoelectric elements.

ln addition to controlling a localized portion of the lamp bulb wall, considerations should be given to the temperature of the remainder ofthe lamp bulb wall, which :tor efficient operation should be at a temperature above the temperature of the localized portion, but which should not be excessively high. When the temperature of the remainder of the lamp bulb wall is excessively higher than that oi the controlled localized portion, the capability of the lamp to maintain a desired lumen output is adversely affected.

Accordingly, an object of our invention is the provision of control means for the thermoelectric spot cooling mechanism which is influenced essentially only by the temperature of the portion oi' the lamp being controlled and the inliuence of other sources ot temperature variation within the luminaire is maintained at a minimum.

another object of our invention is the provision of an efficient thermal Contact between the lamp bulb wall and the spot cooling mechanism without exerting undue pressure or shock on the lamp bulb wall.

A further object of this invention is the provision of means for cooling a spot on the lamp bulb wall which will accommodate various size lamps without developing undue pressure or shock with respect to the bulb Wall of the lamp.

A still further object of this invention is to provide compact and etlicient means for conducting heat from the lamp bulb wall land further, for dissipating this heat from the cooling means.

Still another object of this invention is to utilize the cooling means provided for removing heat from the spot cooling mechanism to control the temperature of the remainder of the lamp bulb wall; and also to accomplish the removal of heat from the spot cooling mechanism and the controlling of the temperature of the lamp bulb wall without contaminating the interior of the luminaire.

The novel features of our invention are set forth in the appended claims. The invention itself together with additional objects and advantages thereof, will be more clearly understood from a reading of the following description in connection with the accompanying drawings in which:

FlG. l is a side elevation or" a luminaire incorporating our invention;

FIG. 2 is a cross sectional view taken along lines 2 2 oi FIG. l and also showing the air low pattern through the luminaire;

FlG. 3 is a bottom plan View of the luminaire with the enclosing transparent plastic cover and the lamps removed;

FlG. 4 is an end view of the spot cooling means and its support bracket;

FlG. 5 is an enlarged front elevation of one of the cooling modules in partial cross section; and

FlG. 6 illustrates the electrical power circuit for the cooling assembly.

For convenience our invention has been illustrated and will be described in connection with a four-lamp fluorescent luminaire fixture, which is its preferred embodiment; however', it should be noted that this discussion and illusvtration with reference to a particular luminaire structure is ntended for illustrative purposes only and not by way or' limitation as modifications and variations of the structural features off the luminaire will occur to those skilled in the art and can be made without departing from the scope of our invention.

A lumiw're l, incorporating our invention, includes an upper metallic housing 2 and a lower plastic enclosing A suitable hinge connection (not cover or globe d. shown) can be provided between the housing and the plastic cover to permit opening of the luminaire to expose the interior thereof. Located at one end of the luminaire 1 isa slipiitter attachment d which receives a support arm 6 for mounting the luminaire in its normal operating position. Four fluorescent lamps 7 are included within the luminaire and positioned approximately at the center of the longitudinal axis of the luminaire and adjacent the lamps 7 is a cooling assembly 8.

With reference to FIG. 2, the lamps '7 are supported from lamp socket assemblies 9 and are aligned horizontally below a reflector 10. The reilector 10 is ixedly attached to support brackets 1l which are in turn connected to the housing 2 by brackets 12. ln this manner, the reflector 10 is tixedly mounted within the luminaire 1 and separates the interior of the luminaire into a lower lamp chamber 13 and an upper ballast chamber 14. Electrical ballasts 16 for energizing the lamps 7 and a power source 17 for energizing the cooling means are contained in the upper ballast chamber. The cooling assembly 8 is positioned at a rectangular opening 18 in the reflector 10, which opening, as will appear more clearly hereinafter, provides access for cooling air from the ballast chamber to the lamp chamber.

The cooling assembly S includes a U-shaped frame l19 having an upper wall 21 and depending side walls 22. Connected to and depending from the upper wall 21 of the frame 19 is a thermoelectrie assembly Z3. Fixed to the top of the upper wall 21. is a support bracket 24. Fixedly connected to and depending from the support bracket 211tis an electric motor 26 having attached thereto a blower fan blade 27. rthe upper wall 2l is provided with a generally circular opening 2S adjacent the blower fan blade 27. The frame 19 can be provided with suitable apertures and strain relief grommets for passage therethrough of electrical leads for electrically connecting the thermoelectric assembly 23 and the electric motor 26 to their power source 17; however, for convenience and clarity the apertures and leads have been eliminated. The power source 17 includes (not shown) a combination of a stepdown transformer to yconvert A.C. line voltage to a low A.C. voltage and suitable half wave rectitiers to provide a low DC. voltage for the thermoelectrie elements.

The thermoelectric :assembly 23 includes four cooling modules 29, one for each lamp 7. Each of the modules 29 includes a cold junction 31 preferably comprising four relatively spaced metal shoes 312, a hot junction 33 preferably in the form of relatively spaced dissipating tins 3d, and Peltier type thermoelectric elements 36. The Peitier type junction elements 35 connect the cold junction and hot junction in heat transfer relationship, with a pair of Peltier elements 36 connecting respective ones of the metal shoes 32 and the heat dissipating tins 34. Each Peltier type couple includes a P-type element and an N-type element, the P-type element having the characteristie of conducting heat in the direction of the current iiow through the element and the Ntype element having the characteristics of conducting heat in reverse of the direction of the current iiowing through the element. Therefore, the heat dissipating ns 3d, the Peltier elements 36 and the metal shoes 32. can be connected in series circuit relationship and heat will be conducted from the metal shoes 32 to the heat dissipating ns 34. A more complete description and illustration of this series circuit connection is disclosed in application Serial No. 859,455 and reliance is placed on that description to complete the disclosure in this application. Spacers 37 and 33 of suitable electrical insulating material are included in each of the modules 29 to maintain a minimum spacing between the heat dissipating ns 34.

The modules 29 are supported between a pair of brackets 39. The brackets 39 are provided at their upper ends with laterally extending anges 41. The ilanges il are suitably apertured and engage the underside of the upper wall 21 of the U-shaped frame 19 and lare ixedly attached to the frame 1.9 by machine screws ft2. The brackets 39 together with the U-shaped frame 19 form an air plenum chamber 4h. A guide member i3 is ixedly attached to the inner side of each of the brackets 39 by screws 44. A spacer 4h is positioned on a screw 47 with a combination spacer te and screw 47 being disposed in a suitable aperture 48 in each of the guide members 43, the combination spacer and screw being capable of vertical movement relative to their respective guide members 43. The apertures 4S are in the nature of clearance holes to permit movement of the modules 29 relative to the lamps for centering and alignment of the modules relative to the lamps. A washer 51 positioned at the head of the screw 47 provides a lower seat for the spacer 46 and also provides a lower seat for a compression spring S2. The upper end of the compression spring 52 is seated against a washer 53 which is positioned beneath each of the guide members 43. Accordingly, the compression spring 52 is confined between the guide member 43 and the washer 51. The upper end of each of the screws 47 extends beyond the end of their respective spacers 46. The outermost heat dissipating ns 34 are each provided with a laterally extending mounting tab 54. These tabs 54 are suitably apertured for passage therethrough of the upper end of the screw 47. Nuts 56 are provided for each of the screws 47 and clamp the mounting tab 54 to the upper end of the spacers 46. Therefore, as can be seen in FIG. 4 the modules 29 are xedly connected to and are movable with the combination spacers 46 and screws 47 relative to the support bracket 39 and in a vertical direction.

Extending laterally on the outer side of each of the support brackets 39 is a mounting bracket 5'7. These mounting brackets engage a frame 5S adjacent the rectangular opening 18 and are xedly connected thereto by machine screws 59. ln this manner the cooling assembly il is tixedly supported on the refiector 1 0 with the modules Z9 extending downwardly through the rectangular opening 18 and disposed to engage localized portions of respective ones of the lamps 7. Furthermore, the thermoelectric spot cooling assembly 23 and the blower fan 7, with its driving motor, are integrated in one assembly S so that they can be installed or removed from the luminaire as a unit.

The modules 29 being spring mounted in the bracket 39, as explained above, can be displaced vertically as the lamps 7 are installed in the luminaire. This provides for a gradual engagement of the lamps 7 with their respective module 29 without the danger of a sharp impact between the lamp and the module which might break the lamp bulb. The lamp 7, on the left as viewed in FlG. 2, has been shown in dotted lines and its cooling module 29 shown in its at rest position to illustrate the amount of travel provided. Furthermore, as can be seen in FIG. 2, when the lamps 7 are installed the springs 52 are compressed slightly so as to constantly urge the module 29 toward engagement with the lamp 7. In this manner a good thermal connection is established between the metal shoes Si?. and the lamp 7 without undue pressure being exerted on the lamp which might create detrimental stresses in the lamp bulb wall. It has also been found desirable to apply a small coating of silicone grease to the underside of the metal shoes 32, i.e. the lamp contacting portion of the metal shoes 32, which in addition to improving the heat transfer relationship between the shoes and the lamp also tends to lubricate the connection and prevent contact of the lamp with sharp or rough edges which could damage the lamp bulb wall.

To provide for precise and accurate temperature control of the cold junctions 31 of the modules 29, so that the current to the modules will cycle to maintain a spot on the lamp bulb wall at a predetermined temperature, a thermostat 61 is included in one of the modules Z9. The thermostatel is mounted atop the cold junction 31 of the module Z9.

The connection of the thermostat 61 in the power circuit is illustrated in FIG. 6. The thermostat 61 controls the supply or power' to the modules 29 to maintain the metal shoes 32 at a proper temperature such that a heat transfer relation will be maintained between the cold junction 31 and their respective localized portions of the lamps 7. The temperature of the metal shoes 32 is dependent upon the temperature of the lamp bulb wall and thereto-re the thermostat 6l, which senses the temperature ot the metal shoes 32, is indirectly controlled by the temperature ol the localized portion of the lamp adjacent the metal shoes 373.

ln order to accurately sense the temperature of the metal shoes and thereby precisely control the ,temperature ot the metal shoes and, correspondingly the temperature of the spot on the lamp bulb wall, the thermostat 6l should not be greatly influenced by other sources ot' temperature variations within the luminaire, eg. the heat stored in the heat dissipating ns 3d, the temperature of the air circulated by the blower Z7, and the temperature ot the remainder of the lamp bulb wall.

hereiore, it is preferred to encapsulate the thermostat @l in a teamed plastic heat insulating body @52. As can be seen in 5, the foamed plastic insulation d2 completely encloses the thermostat 6l and terminates at its upper end slightly above the juncture between the heat dissipating tins 3d and the Peltier elements 36. Each of the modules 29 are provided with the body 62 and preferably the lower margin of the loamed plastic body d2 is specially configured so as to center the metal shoes 32 with respect to the lamps '7, regardless of the diameter of the latter. ln this preferred embodiment, the lower margin of the roamed plastic body d?. is generally arcuate in shape and has its end portions terminating substantially below the under surface of the metal shoes 32. Furthermore, the metal shoes extend beyond the lower margin or' the lower plastic body 62, as can be seen in HG. 5, so that the metal shoes 352 will always be in contact with the lamp bulb wall. The extension of the body 62 below the metal shoes 32 tends to automatically center the module on the lamp bulb wall.

lt should be noted that the thermostat 6l, which rests atop the cold junction Sill, should be electrically insulated from the junction. Preferably a thin piece of milar tape is positioned between the thermostat el and the cold junction, milar tape being chosen because it possesses both good electrical insulating properties and also good heat conducting characteristics so that its incorporation in the module does not adversely atleet the sensing capabilities of the thermostat 6l..

In operation, ieat is transferred from a portion of the lamp bulb wall to the metal shoes from which it is conducted by the Feltier elements to the heat dissipating tins 34. The thermostat monitors the temperature of the portion ot the lamp bulb wall and cycles the operation of the Peltier elements 36 in a manner to maintain the portion of the lamp bulb wall at a predetermined ternperature which will provide optimum light output of each of the lamps '7. Preferably, for operation ot the luminaire in the warmer ambient temperatures, the localized portion of the lamp bulb is maintained in the range 90 to lGS" F. to result in optimum light output of the luminaire. ln the colder ambient temperatures, the modules are not cycled by the thermostat el., but remain cle-energized to prevent over-cooling of the localized portions. The blower 27, upon energization of the motor 2d, directs a stream of cooling air through the heat dissipating .tins to remove heat therefrom. This air is directed downwardly over the modules 29 and passes into the lamp chamber l. It should be noted at this point, that the provision of the oamed plastic insulating body 62 provides the additional advantage in that by insulating the thermostat el from the cooling stream of air the air can be readily directed through the module 2@ and into the lamp chamber t3 for a purpose now to be described.

It will be noted in FlG. 3, that the reflector 1l) is supported from the housing 2 in a manner to provide openings 63 along each side of the reflector. Further, the reflector itl terminates short of the opposed ends of the housing 2 to provide opening dll. Thus the air which is directed through the modules 29 by the blower Z7 is permitted to circulate through the lamp chamber 13 and around the lamps 7 and return to the ballast chamber ld by way of openings 63 and 64. It will also be noted in FIG. 2 that the connection between the housing 2 and the plastic enclosing cover 3 is made through sealing means 6d which provides an air tight connection therebetween. In this manner outside air is prevented from entering the luminaire and the air circulated by the blower Z7 consists only of interior luminaire air, accordingly no dust and dirt is drawn into the luminaire which would deposit on the reilector suriaces and/or the lamps to substantially reduce the lumen output of the luminaire 1. This closed circuit of cooling air not only removes heat from the heat dissipating tins 34 but further in passing over the lamps '7 is operative to cool the portions of the lamps i removed from the spot being cooled to thereby prevent the temperature of those removed portions of the lamp from becoming excessive to adversely affect the lumen maintenance characteristics of the lamps.

Furthermore, the circuit of cooling air passes the air through the upper chamber' i4 and around the ballasts lo. The cooling of the localized portions of the lamps increases the power supplied to the lamps to approximately %to result in optimum light output. The cooling induence of the air passing over the ballasts prevents their exceeding their allowable operating hot spot temperature.

For some installations the luminaire 1 may be called upon to operate in extremely low ambient temperatures. In such a case the danger exists of over cooling by the modules il and the portions of the lamps 7 removed from the spot being controlled. This danger would arise should the blower 27 be allowed to operate continuously. In the lower ambient temperatures it may be desirable to produce a still air condition within the luminaire so that the temperature ot the lamp can be brought up to a proper operating range. Theretore, it is preferable to provide a thermostat 67 which is preferably mounted in the air plenum chamber 4t! so that it is directly exposed to the stream of air directed by the fan 27. This thermostat, as can be seen in FIG. 6, is inthe power circuit to the blower motor and is set so that should the temperature of the stream of cooling air fall below a predetermined temperature the thermostat will turn oil the supply of current to the motor thereby eliminating air circulation and creating a still air condition within the luminaire. Accordingly the interior of the luminaire will be warmed by the lamps 'i and will eventually reach a proper temperature to allow the lamps 7 to operate eticiently; however, should the temperature become excessive the thermostat 67 will operate to energize the blower 27 and thereby `cool interior of the luminaire and the lamps 7 to a proper temperature.

Since with the benefit ot this disclosure and description of our invention modifications and alterations will readily present themselves to those skilled in the art it is intended in the appended claims to cover all modifications, variations and embodiments ot our invention as fall within the true spirit and scope thereof.

lllhaet we claim is:

l. A luminaire comprising, in combination, a housing, a light transmitting cover engaging said housing and forming therewith a hollow enclosure, a reflector coninected to said housing and dividing the interior'thereof into upper and lower chambers, said reflector having an aperture therein opening said upper chamber to said lower chamber, a plurality of fluorescent lamps supported in said lower chamber and extending longitudinally of said reflector, and a cooling assembly supported on said reilector adjacent said aperture in said reliector, said cooling assembly including a blower ian constructed and arranged to provide a stream of cooling air through said aperture in said reflector and a plurality of thermoelectric cooling means and extending through said aperture in said reflector to engage a localized portieri of respective ones of said lamps for cooling and maintaining said localized portion at a predetermined temperature, each of said thermoelectric cooling means including a cold junction in contact with said localized portions, a hot junction for receiving and dissiplating heat and a plurality of Peltier-type thermoelectric elements connecting respective ones of said hot and cold junctions to transfer heat from said cold junctions to said hot junctions, thermally sensitive control means connected to one of said cold junctions and sensitive to the temperature thereof for controlling the transfer of heat from said cold junction to said hot junction, a heat insulating medium enclosing said sensitive control means and a portion of said cold junctions adjacent said connection between said heat sensitive control means and said cold junction so that said control means is influenced substantially only by variations in temperature of said cold junction, means for resiliently mounting said thermoelectric cooling means for vertical movement relative to said lamps and for biasing said cold junctions into engagement with respective ones of said lamps, and a thermostat disposed in said cooling air stream for controlling the energization of said blower fan in accordance with the temperature of said air stream.

2. A luminaire comprising, in combination, a housing, a light transmitting cover sealably engaging said housing and forming therewith a sealed hollow enclosure, a reflector connected in said enclosure and dividing the interior thereof into upper and lower chambers, said reflector having an aperture therein opening said upper chamber to said lower chamber, a plurality of apertures spaced around the margin of said reflector, at least one gaseous discharge lamp supported in said lower chamber and extending longitudinally of said reflector, and a cooling assembly supported at said opening in said reilector, said cooling assembly including rotatably driven blower fan means for directing a stream of air through said aperture in said reflector and means disposed below said blower fan means and adjacent a localized portion of said lamp for conducting heat away from said localized portion to cool and maintain said localized portion at a predetermined temperature, said cooling means also including means for receiving and dissipating heat conducted from said localized portion and heat sensitive control means disposed adjacent said localized portion for controlling the amount of heat conducted away from said localized portion, heat insulating means substantially enclosing said heat sensitive control means Vwith a portion only of said control means exposed to and influenced by the temperature of said localized portion so that said control means is not influenced by other variations in temperature in said luminaire.

3. A luminaire comprising, in combination, a housing, an enclosing light transmitting cover disposed below said housing, a sealed connection between sai-d housing and said cover whereby a sealed enclosure is provided by said housing and said cover, a reflector connected to said housing and extending longitudinally thereof and dividing the interior of said housing into upper and lower chambers, the margins of said reector terminating in spaced relation from said housing and said reflector having an aperture therein opening said upper chamber to said lower chamber, a plurality of iluorescent lamps supported below said reilector and extending longitudinally thereof, and a cool-1 ing assembly connected to said reflector at said aperture in said reflector, said cooling assembly including in said upper chamber a blower fan and means for rotatably driving said blower fan to provide a stream of air through said aperture in said rellector, said cooling assembly also including a plurality of cooling means disposed below said blower fan and each extending through said aperture in said reflector to engage a localized portion of respective ones of said lamps for conducting heat away from said lamp at a controlled rate to cool and maintain said localized portion at a predetermined temperature, said cooling means including means for receiving and dissipating the heat conducted away from said localized portions, whereby a closed circuit of cooling air is provided in said luminaire by said blower fan with cooling air being circulated to and conducting heat away from said heat receiving and dissipating means and the portion of said lamps removed from said localized portions.

4. A lurm'naire comprising, in combination, a housing, an enclosing light transmitting cover disposed below said housing, a sealed connection between said housing and said cover whereby a sealed enclosure is provided by said housing and said cover, a reilector connected in said luminaire and dividing the interior thereof into upper and lower chambers, said reflector having an aperture therein opening said upper chamber to said lower chamber, a plurality of apertures spaced around the margin of said reflector, at least one gaseous discharge lamp supported below and extending longitudinally of said reflector, and a cooling assembly supported at said aperture in said rellector, said cooling assembly including rotatably driven fan means for directing a stream of air through said aperture in said reflector, and means adjacent a localized portion of said lamp for conducting heat away from said localized portion to cool and maintain said localized portion at a predetermined temperature, said cooling means also including means for receiving and dissipating the heat conducted away from said localized portion and being positioned below said fan means in said aperture in said reflector, whereby a closed circuit of cooling air is produced in said luminaire between said upper and lower chambers by said fan means so that heat is conducted away from said heat receiving and dissipating means and the portions of said lamps removed from said localized portions.

5. A luminaire comprising, in combination, a plurality of iluorescent lamps, a cooling module adjacent each of said lamps and each including a cold junction in contact with a localized portion of respective ones of said lamps and at least one thermoelectric couple in contact with each of said cold junctions and operative to conduct heat away from said cold junction, an electric power source connected to said modules and supplying electric power to said thermoelectric couples, at least one of said modules including a thermostat mounted on said cold junction and connected to said power source and controlling the supply of power to said modules in accordance with the temperature of said cold junction so that a heat transfer relationship is maintained between said cold junction and said localized portion to maintain said localized portion at a predetermined temperature, and a heat insulating medium surrounding said thermostat and a portion of said cold junction adjacent the connection between said cold junction and said thermostat, said thermostat being substantially enclosed by said heat insulating medium and being exposed only to variations in temperature of said cold junction.

6. In a luminaire having at least one gaseous discharge lamp, a thermoelectric cooling module including a cold junction adjacent a localized portion of said lamp, means for conducting heat away from said cold junction, and heat sensitive control means mounted on said cold junction and sensitive to the temperature thereof for controlling the conduction of heat from said cold junction so that a heat transfer relationship is maintained between said localized portion and said cold junction and said localized portion of said lamp is maintained at a predetermined temperature, a heat insulating medium surrounding said heat sensitive control means and a portion of said cold junction adjacent the connection between said cold junction and said heat sensitive control means, so that said heat sensitive control means is substantially enclosed by atea,

said heat insulating medium and is exposed only to variations in temperature of said cold junction.

7. In a luminaire having at least one gaseous discharge lamp, thermoelectric cooling means adjacent a localized portion of said lamp for conducting heat away from said localized portion, said cooling means also including heat sensitive control means for controlling the amount ot heat conducted away from said localized portion so that said localized portion will be maintained at a predetermined temperature, heat insulating means substantially enclosing said heat sensitive control means With a portion only of said control means exposed to and iniiuenced by the temperature of said localized portion so that said control means is not iniiuenced by other variations in temperature in said luminaire.

8. The combination which comprises, radiation-generating means comprising a metallic-vapor discharge device desired to be operated under such conditions as would normally cause the operating metallic-vapor pressure within said device to exceed the pressure desired, and cooling means associated with said generating means and comprising a thermoelectric cooling member having a iirst portion acting when energized to cool a selected location within said generating means to reduce the operating metallic-Vapor pressure therein so that it at least approaches the pressure desired and a second portion constructed and arranged to dissipate heat removed from said location, thermostat means in heat exchange relation with said location and operative to control the energization of said first portion in accordance with the temperature oi said location, said thermostat means being therma iy isolated irom said second portion.

9. The combination which comprises, radiation-generating means comprising a low-pressure mercury-vapor discharge device desired to be operated under such conditions as would normally cause the operating mercury-vapor pressure within said device to exceed the pressure desired and cooling means associated with said generating means and comprising a D.C.operable thermoelectric cooling member having when energized a hot junction and a cold junction, the hot junction of said cooling means adapted to have generated heat removed therefrom and the cold junction of said cooling means positioned to cool a selected location Within said generating means to reduce the operating mercury-vapor pressure therein so that it at least approaches le pressure desired, and thermostat means in heat exchange relation with said selected location and operative to control the DC. energization of said cooling means in accordance with the temperature of said selected location, said thermostat means being thermally insulated from said hot junction.

10. In combination, a metallic vapor lamp, a pair of thermoelectric elements having a iirst junction in contact with a portion of said lamp and a second junction spaced from said lamp, a source of electrical energy in circuit with said elements and being of such polarity to cause cooling at said iirst junction, thermostat means in heat exchange relation with said iirst junction and operative to control the iiow of electrical energy to said iirst junction in accordance with the temperature of said lamp portion, said thermostat means being thermally isolated from said second junction.

11. In combination, a metallic vapor lamp, a pair of thermoelectric elements having a first junction in contact with a portion of said lamp and a second junction spaced from said lamp, a source of electrical energy in circuit sse with said elements and of such polarity to cause cooling at said first junction, said second junction incinding heat dissipating means, thermostat means in heat exchange relation with said first junction and operative to control the ilow ot current to said rst junction in accordance With the temperature of said iamp portion, and means for thermally isolating said thermostat means from said second junction.

12. In combination, a metallic vapor lamp, a pair of thermoelectric elements having a rst junction in contact with said lamp and a second junction spaced from said lamp, a source of electrical energy in circuit with said elements and of such polarity to cause cooling at said iirst junction, said second junction including heat dissipating means, thermostat means in heat exchange relation with said rst junction and operative to interrupt the iiow of current to said first junction when the temperature thereof falls -below a predetermined value and heat insulating means disposed between said thermostat means and said second junction.

13. ln combination, a metallic vapor lamp, a pair of thermoelectric elements having a first junction in contact with a localized portion of said lamp and a second junction spaced from said lamp, a source of electrical energy in circuit with said elements and being of such polarity to cause cooling at said iirst junction, control circuit means for said energy source and including thermostat means in heat exchange relation with said rst junction, and thermally isolated from said second junction, said control circuit means being operative to interrupt the i'low of current to said rst junction when the temperature of said localized portion falls below a predetermined value.

14. In combination, a metallic vapor lamp, a pair of thermoelectric elements having a rst junction in contact with said lamp and a second junction spaced from said lamp, a source of electrical energy in circuit with said elements and of such polarity to cause cooling at said first junction, said second junction including heat dissipating means, thermostat means in heat exchange relation with said first junction and operative to interrupt the iiow of current to said first junction when the temperature thereof falls below a predetermined value, and fan means for circulating cooling tluid through said heat dissipating means.

15. In combination, a metallic vapor lamp, a pair of thermoelectric elements havin!Y a iirst junction in contact with a localized portion of said lamp and a second junction spaced from said lamp, a source of electrical energy in series circuit relation with said elements and of such polarity to cause cooling at said first junction, said second junction including heat dissipating means, control circuit means for said energy source and including thermostat means in heat exchange relation with said iirst junction, said control circuit means being operative to interrupt the iiow of current to said iirst junction when the temperature thereof falls below a predetermined vaiue, heat insulating means disposed between said second junction and said thermostat means, and means for circulating cooling fiuid to said heat dissipating means.

References Cited yin the rile of this patent UNITED STATES PATENTS 2,886,699 Hurling May 12, 1959 2,932,753 ArnOtt Apr. l2, 1960 2,933,596 Tolbert Apr.y 19, 1960 

10. IN COMBINATION, A METALLIC VAPOR LAMP, A PAIR OF THERMOELECTRIC ELEMENTS HAVING A FIRST JUNCTION IN CONTACT WITH A PORTION OF SAID LAMP AND A SECOND JUNCTION SPACED FROM SAID LAMP, A SOURCE OF ELECTRICAL ENERGY IN CIRCUIT WITH SAID ELEMENTS AND BEING OF SUCH POLARITY TO CAUSE COOLING AT SAID FIRST JUNCTION, THERMOSTAT MEANS IN HEAT EXCHANGE RELATION WITH SAID FIRST JUNCTION AND OPERATIVE TO 